Solid-state imaging device and electronic camera

ABSTRACT

A solid-state imaging device includes a second image sensor having an organic photoelectric conversion film transmitting a specific light, and a first image sensor which is stacked in layers on a same semiconductor substrate as that of the second image sensor and which receives the specific light having transmitted the second image sensor, in which a pixel for focus detection is provided in the second image sensor or the first image sensor. Therefore, an AF method can be realized independently of a pixel for imaging.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.15/485,596 filed Apr. 12, 2017, which is a continuation of U.S.application Ser. No. 15/088,436 filed Apr. 1, 2016 (now U.S. Pat. No.9,654,709), which is a continuation of U.S. application Ser. No.13/736,204 filed Jan. 8, 2013 (now U.S. Pat. No. 9,385,148), which isbased on and claims priority under 35 U.S.C. 119 from Japanese PatentApplication No. 2012-005270 filed on Jan. 13, 2012. The disclosures ofthe prior applications are hereby incorporated by reference herein intheir entireties.

BACKGROUND 1. Field

The present application relates to a solid-state imaging device and anelectronic camera.

2. Description of the Related Art

Conventionally, a contrast method, a phase-difference AF method, and thelike are known as the technique for realizing high-speed AF(auto-focusing) by using an electronic camera. The contrast method is amethod for detecting a focusing position by using a pixel for imaging.Furthermore, the phase-difference AF method requires a dedicated pixelfor focus detection, and for example, there is known a technique forarranging the pixel for focus detection at some of the pixels forimaging of one image sensor (e.g., see Japanese Unexamined PatentApplication Publication No. 2007-282109). Moreover, there is known atechnique using a dedicated image sensor for focus detection that isarranged separately from an image sensor for imaging (e.g., see JapaneseUnexamined Patent Application Publication No. 2007-011070). In contrast,there is known a technique for stacking two photoelectric conversionelements in layers (e.g., see Japanese Unexamined Patent ApplicationPublication No. 2009-130239).

However, when the pixel for focus detection is arranged at some of thepixels for imaging of an image sensor, a spurious signal of a verticalstripe or a horizontal stripe is apt to be generated, resulting in aproblem in which sophisticated pixel interpolation processing isrequired. Furthermore, when the dedicated image sensor for focusdetection is used, there is a problem in which a complicated opticalsystem for dividing incoming light into the one for an image sensor forimaging and the one for an image sensor for focus detection is required.Moreover, the technique for stacking elements in layers is specific toimage capturing, and neither focus detection nor efficient color arrayis contemplated.

SUMMARY

A solid-state imaging device according to the present embodimentincludes a second image sensor having an organic photoelectricconversion film transmitting a specific light, and a first image sensorwhich is stacked in layers on a same semiconductor substrate as that ofthe second image sensor and which receives the specific light havingtransmitted the second image sensor, in which a pixel for focusdetection is provided in the second image sensor or the first imagesensor.

In particular, the second image sensor is arranged in a specific colorarray as a color filter of the first image sensor.

In addition, a color component of an image signal photoelectricallyconverted by the second image sensor and a color component of an imagesignal photoelectrically converted by the first image sensor are in acomplementary color relationship.

Furthermore, a light-receiving surface of the second image sensor and alight-receiving surface of the first image sensor are arranged on a sameoptical path.

Moreover, the pixel for focus detection is uniformly arranged at allpixels of the second image sensor or the first image sensor.

In addition, the pixel for focus detection includes a photoelectricconversion part which receives at least one of light beams beingobtained by dividing incoming light on each pixel by a pupil-division.

An electronic camera according to the present embodiment is anelectronic camera mounting the solid-state imaging device, in whichthere are provided an optical system which projects incoming light froman object on the second image sensor and the first image sensor beingarranged on a same optical path, an imaging part which performs focuscontrol of the optical system by using a focus detection signal outputfrom the second image sensor and which captures an object image by usingan image signal output from the first image sensor, and a recording partwhich records the object image onto a storage medium.

Furthermore, error correction of a focus detection signal output from apixel of a different color component of the second image sensor isperformed.

Moreover, the imaging part performs focus detection by using a phasedifference detection method after inputting a focus detection signal,which corresponds to an image being obtained by dividing incoming lighton the pixel for focus detection by a pupil-division, from the pixel forfocus detection.

According to the present embodiment, an AF method can be realizedindependently of a pixel for imaging without using sophisticated pixelinterpolation processing and a complicated optical system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an overview of a solid-state image sensor 101.

FIG. 2A is a view showing an example of pixel arrangement.

FIG. 2B is a view showing an example of pixel arrangement.

FIG. 2C is a view showing an example of pixel arrangement.

FIG. 3 is a view showing a circuit example of a first image sensor 102.

FIG. 4 is a view showing a circuit example of a second image sensor 103.

FIG. 5 is a view showing a circuit example of a pixel.

FIG. 6A is a view showing an example of a timing chart.

FIG. 6B is a view showing an example of a timing chart.

FIG. 7 is a view showing a relationship between a layout configurationand a layout cross-section.

FIG. 8A is a view showing a cross-section A-B.

FIG. 8B is a view showing the cross-section A-B.

FIG. 9A is a view showing a cross-section C-D.

FIG. 9B is a view showing the cross-section C-D.

FIG. 10 is a view showing a layout configuration.

FIG. 11A is a view showing an example of the arrangement of alight-receiving part of the second image sensor 103.

FIG. 11B is a view showing an example of the arrangement of thelight-receiving part of the second image sensor 103.

FIG. 11C is a view showing an example of the arrangement of thelight-receiving part of the second image sensor 103.

FIG. 12A is a view showing Modification 1 of the pixel arrangement.

FIG. 12B is a view showing Modification 1 of the pixel arrangement.

FIG. 12C is a view showing Modification 1 of the pixel arrangement.

FIG. 13A is a view showing Modification 2 of the pixel arrangement.

FIG. 13B is a view showing Modification 2 of the pixel arrangement.

FIG. 13C is a view showing Modification 2 of the pixel arrangement.

FIG. 14 is a view showing a configuration example of an electroniccamera 201.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of a solid-state imaging device and anelectronic camera according to the present invention will be describedin detail with reference to the accompanying drawings.

FIG. 1 is a view showing an overview of a solid-state image sensor 101according to the present embodiment. In FIG. 1, the solid-state imagesensor 101 includes a first image sensor 102 that performs photoelectricconversion by using a photodiode, as with an ordinary solid-state imagesensor, and a second image sensor 103 arranged on the same optical pathon an incoming light side of the first image sensor 102. The secondimage sensor 103 includes an organic photoelectric conversion film whichtransmits specific light and photoelectrically converts non-transmittedlight, and the specific light having transmitted the second image sensor103 is received by the first image sensor 102. Here, the first imagesensor 102 and the second image sensor 103 are formed on the samesemiconductor substrate, and each pixel position is in one-to-onecorrespondence to each other. For example, the first row and firstcolumn pixel of the first image sensor 102 corresponds to the first rowand first column pixel of the second image sensor 103.

FIG. 2A is a view showing an example of the pixel arrangement of thesecond image sensor 103. In FIG. 2A, the horizontal direction is set toan x-axis and the vertical direction is set to a y-axis, and thecoordinate of a pixel P is denoted as P(x, y). In an example of thesecond image sensor 103 of FIG. 2A, for each pixel of an odd row, anorganic photoelectric conversion film is alternatively arranged whichphotoelectrically converts the light of Mg (magenta) and Ye (yellow),while for each pixel of an even row, an organic photoelectric conversionfilm is alternatively arranged which photoelectrically converts thelight of Cy (cyan) and Mg (magenta). Then, the light that is notreceived by each pixel is transmitted therethrough. For example, a pixelP(1, 1) photoelectrically converts the light of Mg and transmits thelight of the complementary color (G: green) of Mg. Similarly, a pixelP(2, 1) photoelectrically converts the light of Ye and transmits thelight of the complementary color (B: blue) of Ye, and a pixel P(1, 2)photoelectrically converts the light of Cy and transmits the light ofthe complementary color (R: red) of Cy. Note that, although the detailwill be described later, each pixel of the second image sensor 103includes a pixel for focus detection serving as a pair corresponding toa phase-difference AF method.

FIG. 2B is a view showing an example of the pixel arrangement of thefirst image sensor 102. Note that, each pixel position of FIG. 2B is thesame as that of FIG. 2A. For example, a pixel (1, 1) of the second imagesensor 103 corresponds to the pixel (1, 1) of the first image sensor102. In FIG. 2B, the first image sensor 102 is not provided with a colorfilter or the like, and photoelectrically converts the specific lighttransmitting the second image sensor 103 (the complementary color oflight that is absorbed and photoelectrically converted by the organicphotoelectric conversion film). Accordingly, as shown in FIG. 2C, by thefirst image sensor 102, an image of the color components of G (green)and B (blue) is obtained for each pixel of an odd row, and an image ofthe color components of R (red) and G (green) is obtained for each pixelof an even row. For example, in the pixel P(1, 1), an image of the Gcomponent of the complementary color of Mg of the second image sensor103 is obtained. Similarly, in a pixel P(2, 1) and in a pixel P(1, 2),an image of the B component of the complementary color of Ye and animage of the R component of the complementary color of Cy are obtained,respectively.

In this manner, in the solid-state image sensor 101 according to thepresent embodiment, the second image sensor 103 including an organicphotoelectric conversion film plays the role of the conventional colorfilter, and a complementary color image of the second image sensor 103can be obtained by the first image sensor 102. In the examples of FIGS.2A to 2C, an image with a Bayer array is obtained from the first imagesensor 102. Note that, FIGS. 2A to 2C show examples of the Bayer array,but even with other array, the same results can be achieved by arrangingthe first image sensor 102 and the second image sensor 103 so that eachpixel of the former and each pixel of the latter have a complementarycolor relationship.

In particular, in the solid-state image sensor 101 according to thepresent embodiment, since an organic photoelectric conversion film isused instead of a color filter required for the conventional singleplate type image sensor, the incoming light, which would have beenotherwise absorbed by the color filter, can be effectively utilized bythe second image sensor 103.

Furthermore, in the solid-state image sensor 101 according to thepresent embodiment, since a pixel for imaging is arranged in the firstimage sensor 102 and a pixel for focus detection is uniformly arrangedoverall in the second image sensor 103, there is no need to perform thecomplicated pixel interpolation processing, unlike the conventional artof arranging a pixel for focus detection at some of the pixels forimaging, and thus a signal for focus detection and a color image signalcan be obtained from the second image sensor 103 and the first imagesensor 102, respectively independently.

FIG. 3 is a view showing a circuit example of the first image sensor102. In FIG. 3, the first image sensor 102 has the pixel P(x, y)arranged in two dimensions, a vertical scanning circuit 151, ahorizontal output circuit 152, and an electric current source PW. Notethat, in the example of FIG. 3, for ease of understanding, aconfiguration of 4 pixels of 2 rows by 2 columns is shown, but is notlimiting, and actually a large number of pixels are arranged in twodimensions.

In FIG. 3, the vertical scanning circuit 151 outputs timing signals(ϕTx(y), ϕR(y), ϕSEL(y)) for reading a signal from each pixel. Forexample, timing signals ϕTx(1), ϕR(1), and ϕSEL(1) are supplied to thepixels P(1, 1) and P(2, 1) of the first row. Then, a signal is read fromeach pixel of vertical signal lines VLINE(1) and VLINE(2) connected toelectric current sources PW(1) and PW(2) arranged in each column,respectively, and is temporarily held in the horizontal output circuit152. Then, the signal of each pixel temporarily held in the horizontaloutput circuit 152 for each row is sequentially output to the outside(as an output signal Vout). Note that, although not illustrated in FIG.3, when a signal is read from each pixel to the horizontal outputcircuit 152 via the vertical signal line VLINE(x), a correlated doublesampling (CDS circuit) for removing a variation in the signal betweenpixels, an AD conversion circuit, a digital signal processing circuit,and the like may be arranged.

FIG. 4 is a view showing a circuit example of the second image sensor103. In FIG. 4, the second image sensor 103 has the pixel P(x, y)arranged in two dimensions, a vertical scanning circuit 161, ahorizontal output circuit 162, a horizontal output circuit 163, anelectric current source PW_A, and an electric current source PW_B. Notethat, in the example of FIG. 4, as with FIG. 3, the second image sensor103 includes 4 pixels of 2 rows by 2 columns, but not limited thereto,and actually a large number of pixels are arranged in two dimensions.Furthermore, each pixel P(x, y) of FIG. 4 corresponds to each pixel P(x,y) of FIG. 3. In particular, the second image sensor 103 has, at onepixel position, two photoelectric conversion parts of a light-receivingpart PC_A(x, y) and a light-receiving part PC_B(x, y) each including anorganic photoelectric conversion film, and constitutes a pair of pixelsserving as a pair of the phase-difference AF method.

In FIG. 4, the vertical scanning circuit 161 outputs timing signals(ϕR_A(y), ϕR_B(y), ϕSEL_A(y), and ϕSEL_B(y)) for reading a signal fromeach pixel. For example, timing signals ϕR_A (1) and ϕSEL_A (1) aresupplied to the light-receiving parts PC_A(1, 1) and P_A(2, 1) of thefirst row, and timing signals ϕR_B(1) and ϕSEL_B(1) are supplied to thelight-receiving parts PC_B(1, 1) and P_B (2, 1). Then, the signals ofthe light-receiving parts PC_A(1, 1) and P_A (2, 1) are read out tovertical signal lines VLINE_A(1) and VLINE_A(2) that are connected tothe electric current sources PW_A(1) and PW_A (2) arranged at eachcolumn, respectively, and are temporarily held in a horizontal outputcircuit_A162. The signal of each pixel temporarily held in thehorizontal output circuit_A162 for each row is sequentially output tothe outside (as an output signal Vout_A). Similarly, the signals of thelight-receiving parts PC_B(1, 1) and P_B(2, 1) are read out to thevertical signal lines VLINE_B(1) and VLINE_B(2) that are connected tothe electric current sources PW_B(1) and PW_B(2) arranged at eachcolumn, respectively, and are temporarily held in a horizontal outputcircuit_B162. The signal of each pixel temporarily held in thehorizontal output circuit_B162 for each row is sequentially output tothe outside (as an output signal Vout_B).

In the foregoing, the circuit examples of the first image sensor 102 andthe second image sensor 103 have been described in FIG. 3 and FIG. 4,respectively separately, but actually the first image sensor 102 and thesecond image sensor 103 are formed on the same semiconductor substrateand constitute one solid-state image sensor 101.

Circuit Example of the Pixel of the Solid-State Image Sensor 101

Next, a circuit example of the pixel of the solid-state image sensor 101will be described. FIG. 5 is a view showing a circuit example of onepixel P(x, y) arranged in two dimensions. In FIG. 5, the pixel P(x, y)has a photodiode PD, a transfer transistor Tx, a reset transistor R, anoutput transistor SF, and a selection transistor SEL as a circuit forconstituting the first image sensor 102. The photodiode PD stores acharge corresponding to the amount of light of incoming light, and thetransfer transistor Tx transfers the charge stored in the photodiode PDto a floating diffusion region (FD part) on the output transistor SFside. The output transistor SF constitutes the electric current sourcePW and a source follower via the selection transistor SEL, and outputs,to the vertical signal line VLINE, an electric signal corresponding tothe charge stored in the FD part as an output signal OUT. Note that thereset transistor R resets the charge of the FD part to a power-supplyvoltage V_(CC).

Furthermore, the circuit for constituting the second image sensor 103has a light-receiving part PC including an organic photoelectricconversion film, reset transistors R_A and R_B, output transistors SF_Aand SF_B, and selection transistors SEL_A and SEL_B. The light-receivingpart PC including an organic photoelectric conversion film convertsnon-transmitted light into an electric signal corresponding to theamount of the non-transmitted light, as described in FIG. 2A, andoutputs the resulting signal to the vertical signal lines VLINE_A andVLINE_B as output signals OUT_A and OUT_B via the output transistorsSF_A and SF_B that constitute a source follower with the electriccurrent sources PW_A and PW_B via the selection transistors SEL_A andSEL_B, respectively. Note that the reset transistors R_A and R_B resetthe output signal of the light-receiving part PC to a reference voltageVref. Furthermore, a high voltage Vpc is supplied for operation of theorganic photoelectric conversion film. Here, each transistor includes aMOS_FET.

Here, the operation of the circuit of FIG. 5 is described using timingcharts of FIGS. 6A and 6B. FIGS. 6A and 6B are views showing an exampleof the timing signal of FIG. 5. FIG. 6A is a view showing an operationtiming of the first image sensor 102, in which, first, a selectionsignal ϕSEL becomes “High” at a timing T1 and the selection transistorSEL is turned on. Next, a reset signal ϕR becomes “High” at a timing T2,and the FD part is reset to the power-supply voltage V_(CC) and theoutput signal OUT also becomes a reset level. Then, after the resetsignal ϕR becomes “Low”, the transfer signal ϕTx becomes “High” at atiming T3, and the charge stored in the photodiode PD is transferred tothe FD part, and the output signal OUT starts to change in response tothe charge amount and is then stabilized. Then, the transfer signal ϕTxbecomes “Low”, and the signal level of the output signal OUT to be readfrom a pixel to the vertical signal line VLINE is established. Then, theoutput signal OUT of each pixel read out to the vertical signal lineVLINE is temporarily held in the horizontal output circuit_152 for eachrow, and, after that, is output from the solid-state image sensor 101 asthe output signal Vout. In this manner, a signal is read from each pixelof the first image sensor 102.

FIG. 6B is a view showing an operation timing of the second image sensor103, wherein first, the selection signal ϕSEL_A (or ϕSEL_B) becomes“High” at a timing T11, and the selection transistor SEL_A (or SEL_B) isturned on. Next, the reset signal ϕR_A (or ϕR_B) becomes “High” at atiming T12, and the output signal OUT_A (or ϕOUT_B) is also set to thereset level. Then, immediately after the reset signal ϕR_A (or ϕR_B)becomes “Low” at a timing T13, the charge accumulation of thelight-receiving part PC by an organic photoelectric conversion film isstarted, and the output signal OUT_A (or output signal OUT_B) changes inresponse to the charge amount. Then, the resulting output signal OUT_A(or output signal OUT_B) is temporarily held in the horizontal outputcircuit_A162 (or horizontal output circuit_B163) for each row, and isthen output from the solid-state image sensor 101 as the output signalVout_A (or output signal Vout_B). In this manner, a signal is read fromeach pixel of the second image sensor 103.

A portion (a) of FIG. 7 is an example of the semiconductor layout of thesolid-state image sensor 101. Note that the portion (a) of FIG. 7corresponds to each of the pixel P(1, 1) to the pixel P(2, 2) of FIGS.2A to 2C and FIG. 4 described earlier.

A portion (b) of FIG. 7 is a cross-sectional view of the portion (a) ofFIG. 7 along a cutout line A-B in the horizontal direction on the pixelP(1, 1) and the pixel P(2, 1). Furthermore, FIG. 8A is an enlarged viewof the portion (b) of FIG. 7, and FIG. 8B is a view illustrating thepixel positions along the cutout line A-B for ease of understanding. Thepixel P(1, 1) at the same position of the first image sensor 102 and thesecond image sensor 103 receives incoming light from an object inputfrom a same micro lens ML(1, 1). Here, in FIG. 8A, a wiring layer 301has a three-layer structure, but it may have a two-layer structure ormay have a four or more layer structure. Then, the output signal of thesecond image sensor 103 is extracted from a signal output end 302 viathe wiring layer 301. Note that, on both sides of the signal output end302, there are arranged separation layers 303 and 304. Moreover, at adistance from the separation layers 303 and 304, there are arrangedphotodiodes PD(1, 1) and PD(2, 1).

A portion (c) of FIG. 7 is a cross-sectional view of the portion (a) ofFIG. 7 along a cutout line C-D in the vertical direction on the pixelP(2, 1) and the pixel P(2, 2). Furthermore, FIG. 9A is an enlarged viewof the portion (c) of FIG. 7, and FIG. 9B is a view illustrating thepixel positions along the cutout line C-D for ease of understanding. Thepixel P(2, 1) and pixel P(2, 2) at the same positions of the first imagesensor 102 and the second image sensor 103 receive incoming light froman object input from the same micro lenses ML(2, 1) and ML(2, 2),respectively. Here, FIG. 9B differs from FIG. 8B in that in the pixelP(2, 1) of the second image sensor 103, the light-receiving part ispupil-divided into the light-receiving part PC_A(2, 1) and thelight-receiving part PC_B(2, 1), and in that in the pixel P(2, 2), thelight-receiving part is pupil-divided into the light-receiving partPC_A(2, 2) and the light-receiving part PC_B(2, 2). Then, thelight-receiving part PC_A(2, 1) and the light-receiving part PC_B(2, 1)can receive an image, serving as a pair, at a pupil position of theoptical system, respectively, and perform focus detection by using aphase-difference AF method. Similarly, the light-receiving part PC_A(2,2) and the light-receiving part PC_B(2, 2) receive an image, serving asa pair, at the pupil position of the optical system, respectively. Notethat, since the phase-difference AF method is a well-known technique,the detailed description thereof is omitted.

Here, in FIG. 9A, the wiring layer 301 of FIG. 8A corresponds to awiring layer 301A and a wiring layer 301B. The wiring layer 301A outputsa signal of the light-receiving part PC_A(2, 1) of an organicphotoelectric conversion film to the signal output end 305A, and thewiring layer 301B outputs a signal of the light-receiving part PC_B(2,1) of an organic photoelectric conversion film to the signal output end305B. In the wiring layer 301 of FIG. 8A, only one wiring layer isvisible because the wiring layer 301A and the wiring layer 301 B overlapwith each other. Similarly, a signal of the light-receiving part PC_A(2,2) of an organic photoelectric conversion film of the pixel P(2, 2) isoutput to a signal output end 306A, and a signal of the light-receivingpart PC_B(2, 2) is output to a signal output end 306B. Then, in areadout circuit 307, readout circuits such as an output transistor, aselection transistor, a reset transistor, and the like are arranged, inwhich the signal of each pixel is output to the outside from thesolid-state image sensor 101.

FIG. 10 is an enlarged view of the layout drawing of the pixel P(1, 1)of the portion (a) of FIG. 7. In FIG. 10, for the circuit arrangedaround the photodiode PD, a hatched portion indicates a gate electrode,and white portions on both sides of the gate electrode indicate an NMOStype transistor including an n region. In FIG. 10, the charge stored inthe photodiode PD of the first image sensor 102 is transferred to the FDpart when the transfer signal ϕTx is supplied to the gate electrode ofthe transfer transistor. The FD part is connected to the gate electrodeof the output transistor SF, in which the transferred charge isconverted into an electric signal, and when the selection signal ϕSEL issupplied to the gate electrode of the selection transistor SEL, theconverted electric signal is read out to the vertical signal line VLINE.Note that, when the reset signal ϕR is supplied to the gate electrode ofthe reset transistor R, the charge of the FD part is reset to thepower-supply voltage V_(CC).

In contrast, in FIG. 10, an electric signal output from a transparentelectrode of the light-receiving part PC_A(1, 1) of an organicphotoelectric conversion film is connected to the gate electrode of theoutput transistor SF_A, and when the selection signal ϕSEL_A is suppliedto the gate electrode of the selection transistor SEL_A, the electricsignal is read out to the vertical signal line VLINE_A. Similarly, anelectric signal output from the transparent electrode of thelight-receiving part PC_B(1, 1) is connected to the gate electrode ofthe output transistor SF_B, and when the selection signal ϕSEL_B issupplied to the gate electrode of the selection transistor SEL_B, theelectric signal is read out to the vertical signal line VLINE_B. Notethat, when the reset signal ϕR_A (or ϕR_B) is supplied to the gateelectrode of the reset transistor R_A (or R_B), the signal voltage ofthe light-receiving part PC_A(1, 1) (or PC_B(1, 1)) is reset to thereference voltage Vref. Note that, in the organic photoelectricconversion film, the high voltage Vpc for extracting an electric signalcorresponding to an incoming light quantity from an opposing transparentelectrode is supplied to a transparent electrode on an incoming lightside.

As described above, the solid-state image sensor 101 according to thepresent embodiment has the first image sensor 102 performingphotoelectric conversion by using a conventional photodiode and thesecond image sensor 103 performing photoelectric conversion by using anorganic photoelectric conversion film, wherein a signal for imaging canbe acquired from the first image sensor 102 and a signal for focusdetection corresponding to a phase-difference AF method can be acquiredfrom the second image sensor 103.

Therefore, in the solid-state image sensor 101, there is no need toarrange a pixel for focus detection at some of the pixels for imaging,unlike the conventional art, and there is no degradation in imagequality due to a spurious signal of a vertical stripe or a horizontalstripe, and sophisticated pixel interpolation processing is notrequired. In addition, since the first image sensor 102 for imaging andthe second image sensor 103 for focus detection are stacked in layers soas to use incoming light of the same micro lens, a complicated opticalsystem for dividing the incoming light into the light for an imagesensor for imaging and the light for an image sensor for focus detectionis not required, unlike the conventional art. In particular, because thesolid-state image sensor 101 according to the present embodiment doesnot require an optical device such as a prism or a mirror, while usingtwo image sensors of the first image sensor 102 and the second imagesensor 103, the arrangement and design of an optical system inconfiguring a camera are easy. Furthermore, in a dual-plate type imagingsensor using a prism, a mirror, and the like, adjustment and the like ofthe optical path length between two image sensors is indispensable,while in the solid-state image sensor 101 according to the presentembodiment, the adjustment is not required because there is one opticalpath.

Moreover, the second image sensor 103 and the first image sensor 102 candetect color components having a complementary color relationship witheach other, and the organic photoelectric conversion film of the secondimage sensor 103 can also be used as a color filter of the first imagesensor 102, and incoming light can be efficiently used without beingwasted.

In this manner, the solid-state image sensor 101 according to thepresent embodiment can realize a phase-difference AF method allowing forhigh-speed operation, without using sophisticated pixel interpolationprocessing and a complicated optical system. Here, in the embodiment, aphase-difference AF method capable of finding a focusing position athigh speed is realized using the second image sensor 103, but a focusingposition may be found by a contrast method through the use of the secondimage sensor 103. The contrast method is a method including the stepsof: moving a focus lens while detecting the contrast of an image; andsetting the position of a focus lens having the highest contrast, to afocusing position.

Note that, when the contrast method is used, the contrast may becalculated by adding two light-receiving parts (e.g., PC_A(x, y) andPC_B(x, y) of FIG. 1 1A) provided in each pixel, or the light-receivingpart of a pixel of the second image sensor 103 may be set to onelight-receiving part without being divided.

In the above example, as shown in FIG. 11A, the light-receiving partsPC_A(x, y) and PC_B(x, y) serving as a pair corresponding to thephase-difference AF method are arranged in each pixel P(x, y) of thesecond image sensor 103. Then, both the two light-receiving parts ofeach pixel have been described as outputting a signal as a focusdetection signal, but are not limited thereto. For example, twolight-receiving parts of each pixel may be constructed so that a signalis output only from either one of light-receiving parts. In this case,light-receiving parts, where adjacent pixels are read, arelight-receiving parts at mutually different positions of twolight-receiving parts. In this manner, read-out drive of a signal can beperformed in a conventional manner.

Furthermore, as an alternative method, as shown in FIG. 11B, only a halfof the light-receiving part PC_A(x, y) or the light-receiving partPC_B(x, y) may be arranged in one pixel P(x, y). That is, in FIG. 11B,AF control by the phase difference detection method can be performed, inwhich the pixel P(1, 1) having the light-receiving part PC_A(1, 1)arranged on the left side and the pixel P(2, 1) having thelight-receiving part PC_B(2, 1) arranged on the right side are paired.

Alternatively, as shown in FIG. 11C, the pixels for focus detectionwhose pupil division directions are various directions such as avertical direction, a horizontal direction, and a diagonal direction,may exist mixedly. In each case, the solid-state image sensor 101according to the present embodiment captures a signal for imaging by thefirst image sensor 102 and captures a signal for focus detection by thesecond image sensor 103, and thus focus detection by high-speedphase-difference AF can be performed at any position in a captured imagewithout affecting the image quality of the captured image.

Here, in the second image sensor 103, as described in FIGS. 2A to 2C,since the pixels corresponding to three colors of Mg, Ye, and Cy existmixedly, a signal for focus detection obtained from a pixel of adifferent color component might differ. Therefore, in performing focusdetection, focus detection by the phase-difference AF method may beperformed utilizing a signal for focus detection obtained from a pixelof the same color component. For example, in the case of FIG. 2A, only asignal for focus detection obtained from a pixel (a pixel of an oddnumber column in the case of an odd row, and a pixel of an even numbercolumn in the case of an even row) of Mg of a large number of pixels isused. Alternatively, an error between the pixels corresponding to threecolors of Mg, Ye, and Cy (a variation in sensitivity between pixels, avariation (DC offset) in reference level, or the like) is measured inadvance, and error correction may be made when performingphase-difference AF processing.

Furthermore, the output signal of the second image sensor 103 may beutilized not only for focus detection but also for white balancecontrol.

Modification 1

FIGS. 12A to 12C are views showing Modification 1 of the color array ofa pixel described in FIGS. 2A to 2C. In the example of FIGS. 2A to 2C,the organic photoelectric conversion film of the second image sensor 103is adapted to correspond to three colors of Mg, Ye, and Cy, and an imagesignal of three colors of R, G, and B can be detected by the first imagesensor 102. However, as shown in FIGS. 12A to 12C, the organicphotoelectric conversion film of the second image sensor 103 maycorrespond to three colors of R, G, and B, and an image signal of threecolors of Mg, Ye, and Cy may be detected by the first image sensor 102.Note that, even in this case, a color component the first image sensor102 photoelectrically converts and a color component the second imagesensor 103 photoelectrically converts have a complementary colorrelationship with each other.

Modification 2

FIGS. 13A to 13C are views showing Modification 2 of the color array ofa pixel described in FIGS. 2A to 2C. In the examples of FIGS. 2A to 2C,a light-receiving part serving as a pair corresponding to thephase-difference AF method is arranged in each pixel of the second imagesensor 103, while in the modifications of FIGS. 13A to 13C, alight-receiving part serving as a pair corresponding to thephase-difference AF method is arranged in some of the pixels of thesecond image sensor 103. Therefore, the circuit size of the solid-stateimage sensor 101 can be reduced.

Example of Electronic Camera

Next, an example of an electronic camera 201 mounting the solid-stateimage sensor 101 is shown in FIG. 14. In FIG. 14, the electronic camera201 includes an optical system 202, the solid-state image sensor 101, animage buffer 203, an image processing part 204, a controller 205, adisplay part 206, a memory 207, an operation part 208, and a memory cardIF209.

The optical system 202 forms an object image on the solid-state imagesensor 101. The solid-state image sensor 101 has the first image sensor102 and the second image sensor 103, as described earlier, a signal forimaging captured by the first image sensor 102 is taken in the imagebuffer 203, and a signal for focus detection acquired by the secondimage sensor 103 is input to the controller 205. The controller 205controls the whole electronic camera 201 in response to a user operationusing the operation part 208. For example, when a release button of theoperation part 208 is half-pressed, the controller 205 performs focusdetection by the phase-difference AF method through the use of thesignal for focus detection obtained from the second image sensor, andcontrols the focusing position of the optical system 202. Then, when auser fully presses the release button of the operation part 208, thecontroller 205 takes an image captured by the first image sensor 102after the focus control, in the image buffer 203. Furthermore, the imagetaken in the image buffer 203 is subjected to white balance processing,color interpolation processing, contour enhancement processing, gammacorrection processing, and the like by the image processing part 204,and is displayed on the display part 206 or stored into the memory card209 via the memory card IF209.

Note that, when a contrast method is used, the second image sensor 103outputs a signal for imaging, as with the first image sensor 102. Then,the controller 205 moves the focus lens of the optical system 202 whiledetecting the contrast of the signal for imaging which the second imagesensor 103 outputs, and obtains a position of the focus lens, where thehighest contrast is obtained, and sets this position to the focusingposition.

In this manner, by mounting the solid-state image sensor 101 accordingto the present embodiment on the electronic camera 201, there is no needto perform sophisticated pixel interpolation processing by the imageprocessing part 204 or to cause the optical system 202 to have acomplicated configuration in which incoming light is divided, and thephase-difference AF method allowing for high-speed operation can berealized.

The many features and advantages of the embodiments are apparent fromthe detailed specification and, thus, it is intended by the appendedclaimed to cover all such features and advantages of the embodimentsthat fall within the true spirit and scope thereof. Further, sincenumerous modifications and changes will readily occur to those skilledin the art, it is not desired to limit the inventive embodiments to theexact construction and operation illustrated and described, andaccordingly all suitable modifications and equivalents may be resortedto, falling within the scope thereof.

What is claimed is:
 1. A solid-state imaging device comprising: a secondimage sensor including an organic photoelectric conversion filmtransmitting a specific light; and a first image sensor which is stackedin layers on a same semiconductor substrate as that of the second imagesensor and which receives the specific light having transmitted thesecond image sensor, wherein a pixel for focus detection is provided inone of the second image sensor and the first image sensor.
 2. Thesolid-state imaging device according to claim 1, wherein the secondimage sensor is arranged in a specific color array as a color filter ofthe first image sensor.
 3. The solid-state imaging device according toclaim 2, wherein a color component of an image signal photoelectricallyconverted by the second image sensor and a color component of an imagesignal photoelectrically converted by the first image sensor are in acomplementary color relationship.
 4. The solid-state imaging deviceaccording to claim 1, wherein a light-receiving surface of the secondimage sensor and a light-receiving surface of the first image sensor arearranged on a same optical path.
 5. The solid-state imaging deviceaccording to claim 2, wherein a light-receiving surface of the secondimage sensor and a light-receiving surface of the first image sensor arearranged on a same optical path.
 6. The solid-state imaging deviceaccording to claim 3, wherein a light-receiving surface of the secondimage sensor and a light-receiving surface of the first image sensor arearranged on a same optical path.
 7. The solid-state imaging deviceaccording to claim 1, wherein the pixel for focus detection is uniformlyarranged at all pixels of one of the second image sensor and the firstimage sensor.
 8. The solid-state imaging device according to claim 2,wherein the pixel for focus detection is uniformly arranged at allpixels of one of the second image sensor and the first image sensor. 9.The solid-state imaging device according to claim 3, wherein the pixelfor focus detection is uniformly arranged at all pixels of one of thesecond image sensor and the first image sensor.
 10. The solid-stateimaging device according to claim 1, wherein the pixel for focusdetection includes a photoelectric conversion part which receives atleast one of light beams being obtained by dividing incoming light oneach pixel by a pupil-division.
 11. The solid-state imaging deviceaccording to claim 2, wherein the pixel for focus detection includes aphotoelectric conversion part which receives at least one of light beamsbeing obtained by dividing incoming light on each pixel by apupil-division.
 12. The solid-state imaging device according to claim 3,wherein the pixel for focus detection includes a photoelectricconversion part which receives at least one of light beams beingobtained by dividing incoming light on each pixel by a pupil-division.13. An electronic camera mounting the solid-state imaging deviceaccording to claim 1, wherein there are provided: an optical systemwhich projects incoming light from an object on the second image sensorand the first image sensor being arranged on a same optical path; animaging part which performs focus control of the optical system by usinga focus detection signal output from the second image sensor and whichcaptures an object image by using an image signal output from the firstimage sensor; and a recording part which records the object image onto astorage medium.
 14. An electronic camera mounting the solid-stateimaging device according to claim 2, wherein there are provided: anoptical system which projects incoming light from an object on thesecond image sensor and the first image sensor being arranged on a sameoptical path; an imaging part which performs focus control of theoptical system by using a focus detection signal output from the secondimage sensor and which captures an object image by using an image signaloutput from the first image sensor; and a recording part which recordsthe object image onto a storage medium.
 15. An electronic cameramounting the solid-state imaging device according to claim 3, whereinthere are provided: an optical system which projects incoming light froman object on the second image sensor and the first image sensor beingarranged on a same optical path; an imaging part which performs focuscontrol of the optical system by using a focus detection signal outputfrom the second image sensor and which captures an object image by usingan image signal output from the first image sensor; and a recording partwhich records the object image onto a storage medium.
 16. The electroniccamera according to claim 13, wherein performing error correction of afocus detection signal output from a pixel of a different colorcomponent of the second image sensor.
 17. The electronic cameraaccording to claim 14, wherein performing error correction of a focusdetection signal output from a pixel of a different color component ofthe second image sensor.
 18. The electronic camera according to claim15, wherein performing error correction of a focus detection signaloutput from a pixel of a different color component of the second imagesensor.
 19. The electronic camera according to claim 13, wherein theimaging part performs focus detection by using a phase differencedetection method after inputting a focus detection signal from the pixelfor focus detection, the focus detection signal corresponds to an imagebeing obtained by dividing incoming light on the pixel for focusdetection by a pupil-division.
 20. The electronic camera according toclaim 14, wherein the imaging part performs focus detection by using aphase difference detection method after inputting a focus detectionsignal from the pixel for focus detection, the focus detection signalcorresponds to an image being obtained by dividing incoming light on thepixel for focus detection by a pupil-division.
 21. The electronic cameraaccording to claim 15, wherein the imaging part performs focus detectionby using a phase difference detection method after inputting a focusdetection signal from the pixel for focus detection, the focus detectionsignal corresponds to an image being obtained by dividing incoming lighton the pixel for focus detection by a pupil-division.